The present invention relates to a counterweight support for a resonantly driven tool such as a pavement breaker.
U.S. Pat. No. 4,340,255 describes a vertical impact system used to break the pavement or tamp down the ground underlying a mobile vehicle. The vehicle includes a resonant beam supported at its nodes and excited at one end near its resonant frequency. A tool projects downwardly from the output end of the beam to break the pavement or tamp down the ground. A large weight is superimposed over the forward node of the beam to counteract the reaction forces of the tool striking the underlying surface. The weight is suspended from the vehicle so that the reaction forces are not transmitted by the weight to the vehicle, isolating the vehicle itself from the reaction forces.
The impact system design of U.S. Pat. No. 4,340,255, has been found to be quite useful, but there have been various problems in implementing the design concept. Specifically, gross movement of the weight relative to the forward node must be prevented, because such movement results in the weight bearing down on the beam at some distance from its actual node. The beam is essentially stationary at its node, but vibrating everywhere but the node, and even a small movement of the weight relative to the node position greatly increases the vibratory forces imparted to the vehicle. However, slight movement must be allowed between the beam and the weight because some small vibration of the beam relative to the weight is inevitable, even if all attempts are made to support the beam exactly at the node position.
Relatively large reaction forces are imparted to the weight by the tool through the beam. The support system must prevent gross movement of the weight relative to the beam, while permitting slight movement, and still accomplish the transmission of the relatively large forces. The pad assembly connecting the weight to the beam, and the pivotal support of the weight at a position above the resonant beam, as described in the referenced patent, have been found less effective than desired in accomplishing these objectives.